How to Backup IMAC With Easy Steps Through Time Machine

1. Turn on Time Machine.
The first time you connect the external hard drive to your Mac, Time Machine will ask if you’d like to use it for backups.

Click Use as Backup Disk and System Preferences will open to display Time Machine preferences.

From now on, Time Machine will do the rest; your first backup will begin automatically in a few minutes.

2. Exclude some items to conserve disk space.
What if you don't want to back up everything on your computer? For example, you might want to exclude your Applications folder from backups, and just reinstall apps from their original CDs if you drive kicks the bucket or if you upgrade later. Click the Options button in the Time Machine preferences window and add files and folders to the "Do not back up" list by clicking the + (plus sign) button. To exclude your Applications folder, select your Mac's hard drive, then the Applications folder, and click Exclude.

If you change your mind later, you can always remove items from this list by clicking the - (minus) button, and those items will be included in the next backup.

When your first Time Machine backup starts, a new window appears on your desktop to let you know things are going. You can close System Preferences now; it won't affect the backup.

4. Ready, Set, Wait
Expect the first backup to take a long time since everything on your Mac is being copied. After the first backup, Time Machine will automatically back up incremental changes to your files every hour for as long as you leave the backup drive connected to your Mac. Future backups will only copy files that are new or have changed, so they'll take less time.

In Time Machine's preferences window, you’ll see the option to show Time Machine's status in the menu bar. Time Machine’s menu bar icon lets you access Time Machine preferences and perform backups any time you want, so you don’t have to wait to back up important files.